The proposed research deals with the structure, function and metabolism of nuclear proteins in intestinal epithelial cells - with particular attention to changes in chromosomal proteins during early stages of colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH). The objective is to relate events in carcinogenesis to changes in DNA-associated proteins concerned with transcriptional control and with DNA synthesis. Experimental approaches begin with isolations of discrete nuclear fractions derived from different cell types in the colonic epithelium. The methods allow a separation of nuclei at different stages of differentiation in the different layers of the crypts and luminar surface of normal, preneoplastic and tumor tissues. The acidic (non-histone) proteins of the various nuclear types are being analyzed in terms of the heterogeneity, molecular size distribution, rates of synthesis and phosphorylation, DNA-binding affinities, specific interactions with cyclic nucleotides, effects on transcription, response to carcinogens, and control of nuclear activity by Vitamin A and Vitamin D. Characteristic changes in nuclear proteins ensuing soon after exposure to the carcinogen, DMH, are being detected in animals long before morphological indications of malignancy. Two classes of nuclear protein have been found to accumulate selectively in the nuclei of colonic epithelial cells during tumor induction by DMH. Similar proteins have now been detected in human colonic tumors and in cell lines derived from human adenocarcinomas. We propose to isolate and characterize these proteins and to prepare specific antibodies against them. High-resolution immunological techniques will be used for studies of their intracellular and chromosomal localization. The immunological detection of these proteins in single cells may constitute the basis for an early diagnosis of preneoplastic changes. Modifications of DNA-binding proteins by carcinogens with alkylating functions are also under investigation.